rikhemi

This a question about the rpms. When your shifting at 9k rpm, and the red light flashes, that is too late right. Is it best to shift at 8.8rpm, or to wait till I see the red flashing to shift. HOw can i get the most power out of the engine. Thanks

kkyntmoon

shift right at the point of redline!
you must be quick!

ruexp67

[QUOTE]Originally posted by rikhemi

RACER

[QUOTE]Originally posted by rikhemi
This a question about the rpms.

johninator

To maximize the engines acceleration performance, it is almost 99% of the time more beneficial to shift at redline than to shift earlier. This is because of gearing. Even if your torque or HP drops near redline, the multiplier drop from the next gear will be less than the keeping it at the lower gear even if HP drops. If it happens the other way around then you should shift earlier. You can calculate this from a engine dyno plot.

RACER

Ok, I just did some calculations with a speed chart. If you were to shift from 2nd gear at 8,700 rpm's into 3rd, your engine rpm's would drop to exactly 6,300 rpm's. If you shifted from 2nd gear at 9,000 rpm's into 3rd, then your engine rpm's would drop to 6,520 rpm's which is 220 rpm's higher than if you shifted at only 8,700 rpm's.

I performed the same calculations shifting from 3rd to 4th gear. Shifting from 3rd to 4th at 8,700 rpm's will drop the rpm's to 6,820 rpm's. The same gear change at 9k will drop the rpm's to 7,055 rpm's which is 235 rpm's higher than if you were to shift at only 8,700 rpm's.

Being that the F20C doesn't come alive untill your reving at least 6,500-7,000 rpm's, the calculations I performed clearly show an advantage of shifting at 9,000 rpm's as it puts you closer to were the power is earlier.

johninator

Here is something you can use handily:

S2000 Gearing and Speed Calculations

johninator

[QUOTE]Originally posted by RACER
Ok, I just did some calculations with a speed chart.

RACER

What the hell are you talking about? Thats what I said, but I used english.

johninator

Just to add a few more examples. I got a dyno chart from the stock EVO that came from Sport Compact Car. This example comes close to having to shift early because of the massive torque drop from 4200 to 7000RPM. Where it drops from 250ft-lbs to 150ft-lbs. A total of ~40% from the top. More particularly 6000-7000RPM where it drops from 200ft-lbs to 150ft-lbs ~25%. If your next gear higher lands at the torque*gear multiplier which is higher than the torque drop*lower gear then its benefitial to shift early and land it back near peak torque at around 4000RPM +- 500RPM. However, each gear drop is usually around ~30% so at around 175 ft-lbs you may want to shift early if it can land you at a torque level 30% greater. Like the stock EVO motor the 350Z line of motors 3.5l V6 have these bell shape torque curves through out its RPM range as well.

The S2000 does not decline that much per 1000RPM where it keeps it flat at the top. One of the best at keeping torque up at higher RPMs is the current Porsche 911 N/A where it only drops ~2-3% at peak per 1000RPM from 3500RPM to 7000RPM. Though it may have similar max torque as the 350Z or the EVO, it is no where close to the 911's performance to redline.